(in millions)
2011
2010
Balance as of January 1,
$
138.8
138.2
Accretion expense
0.3
0.4
Accretion recorded as a regulatory asset/liability
3.8
3.7
Settlements
(1.1
)
(5.5
Change in estimated cash flows
(2.9
—
Balance as of June 30,
138.9
136.8
Schedule of asset retirement obligation.